The aim is to determine how action potentials cause contraction in amphibian and mammalian skeletal muscle. Various voltage-clamp techniques will be used to study (1) ionic channels contributing to electrical excitability especially in mammalian muscle fibres (2) the potential-dependence and kinetics of contractile activation, (3) the role of non-ionic displacement currents in the regulation of contraction. Pharmacological modifications of the excitation-contraction coupling mechanism will be investigated, combining electrical and mechanical studies on intact muscles fibres with measurements on "skinned" skeletal muscle fibres.